(a) Field of the Invention
The present invention relates to an engine, more particularly, a method for controlling a continuous variable valve timing apparatus that variably controls opening and closing timing of intake and exhaust valves in an engine.
(b) Description of the Related Art
Generally, a continuous variable valve timing (CVVT) apparatus changes opening and closing timing of intake and exhaust valves by changing phase angle of a camshaft that controls opening and closing of the intake and exhaust valves, according to an engine speed and load state of a vehicle. If the CVVT apparatus is used in a vehicle, ignition timing of the air-fuel mixture can be controlled effectively. Therefore, exhaust gas and fuel consumption may be reduced, and engine performance may improve.
A conventional method for controlling a continuous variable valve timing apparatus is realized by a feedback control method. That is, the CVVT is controlled by applying a current according to a difference between a current phase angle of the camshaft and a target phase angle of the camshaft to an electric clutch for controlling phase angle of the camshaft every predetermined time interval.
However, according to the conventional method for controlling a continuous variable valve timing apparatus, there is a problem that control timing is delayed since the phase angle of the camshaft is controlled based on feedback control.
In addition, since the phase angle of the camshaft changes according to the temperature of engine oil and engine speed, it is difficult to precisely control valve timing.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.